A log is the partial trunk of a tree whose configuration has developed over years of growth, influenced by a number of factors, such as terrain, environment, and weather. Each log is different and is more or less tapered from one end to the other. The cross section varies from generally circular to generally elliptical. It is often bowed and even more often blemished with a variety of defects including concavaties, splits, and the like. Lumber is produced from these irregular log configurations which lumber consists of regularly shaped boards of specified length, width, and thickness. determining the optimum lumber production from each irregularly shaped log is important and is what this invention is about.
Logs are processed by the thousands over a period of a single one-day shift of lumber production. Correct alignment and positioning will enable increased utilization of the log. Such increased utilization may be the result of more lumber pieces produced or a better mix of lumber pieces which, in either case, produces higher value of lumber produced from a single log. Because such increased log utilization is multiplied by the thousands of logs processed in a single shift, the attainment of the correct alignment and positioning of logs is of great importance. Consequently, log analyzing, log handling, and log cutting apparatus have been developed to a high degree of sophistication.
In a typical log breakdown system, a log is first scanned and computer analyzed to determine the optimum configuration of lumber pieces that will fit the log configuration. The log is then preliminarily shaped to remove the wood material on the rounded sides that does not fit into a board (referred to herein as excess material). For example, the log will be passed through chippers that remove this material and produce flat surfaces on the two opposed sides of the log. Slabs or flitches are then cut from the two sides. (As used herein the terms slabs and flitches are interchangeably used to refer to the initial board width cut from each side of a log or cant.)
The remaining center section having flat sides and rounded top and bottom is referred to as a center cant and is intentionally sized to produce a precise number of specific lumber pieces. In a subsequent operation, the cant is rolled 90 degrees, and the newly provided curved or rounded sides (previously the top and bottom) are chipped as before to remove the excess material and produce opposed flat sides. It is then passed through a saw array and sawn; e.g. into one-by-fours and two-by-fours. (The logs processed in the initial breakdown, and the center cants processed in a secondary breakdown are collectively referred to herein as log segments.)
In the processes just described, the side slabs or flitches from the full log have wane edges. Wane is that area that ends up on a section sawed from a log that was a portion of the outer surface of the log. The flitches being a full width section sawn from the log includes the irregularly curved section of the log's periphery along each side edge and thus each side edge of the flitch is wane area. Lumber specifications (wane rules) allow only a specified amount of wane area to be left on the board and still be acceptable in grade. It is highly desirable to be able to precisely comply with the wane rules leaving neither too much nor too little of the wane area for that lumber grade. The side flitches are typically directed to an edger which precisely cuts the straight edges desired for a finished board and in the process cuts off the unacceptable wane area from the wane edges.
A similar process is requred for at least the outer boards sawn from the center cant. Even though four flat sides are provided on the center cant following the chipping operation, the corners have wane and thus wane areas appear on the outside corners of the outside boards cut from the cant. These wane areas must be edged in the same manner as described above.
The handling apparatus and the controls for setting the saws, chippers, and edgers must be precise. Furthermore, they must be rapidly adjustable from log to log to accommodate the differences in log sizes and configurations.